Water-absorbing resins are widely used in water-retaining agents, dehydrating agents, sludge coagulants and other consumer products. Water-absorbing resins are available in a variety of forms, including substituted and unsubstituted natural and synthetic polymers, such as starch/acrylonitrile graft polymers, carboxymethylcellulose, crosslinked polyacrylates, sulfonated polystyrenes, hydrolyzed polyacrylamides, polyvinyl alcohols, polyethylene oxides, polyvinylpyrrolidones, and polyacrylonitriles.
The most commonly used polymer for absorbing electrolyte containing aqueous fluids is partially neutralized polyacrylic acid (PAA), i.e., containing about 50% to 100%, neutralized carboxyl groups. An exemplary commercially available material is poly(acrylic acid) partial sodium salt from Sigma Aldrich Corporation, St. Louis, Mo.
In addition commercially available polymer fibrous materials are: REON™ 200 from Absorbent Technologies, Beaverton, Oreg.; and Water-Lock® 400 from Grain Processing Corporation, Muscatine, Iowa.
Such water-absorbing resins are termed “superabsorbent polymers,” or SAPs, and typically are lightly cross-linked hydrophilic linear or hydrophilic polymers. SAPs are disclosed in Goldman, et al., U.S. Pat. Nos. 5,669,894 and 5,599,335. US2008/250916 describes barge units with bags containing absorbent fibrous material. US2009/163365 describes a water-swellable material comprising a crosslinked polymer matrix containing inorganic particles. US2009/274519 describes a water-fillable flood control device. US2011/297575 describes a bag containing water-absorbent for retaining soil on slopes. U.S. Pat. No. 6,524,670 describes a double layered bag containing an absorbent. US2003/170406 describes a specialized device containing a water absorbent. US2005/277548 describes a water absorbent containing grafted acrylonitrile and styrene. GB 2438613A describes a specially designed bag for water absorbents.
SAPs can differ in their chemical identity, but all SAPs are capable of absorbing and retaining various amounts of aqueous fluids equivalent to multiple times their own weight but not beyond. Presently available SAPs can absorb distilled water up to one hundred times their own weight.
Conventional SAPs undergo surface swelling when wetted with a fluid such that continued transport of the fluid into the cross-linked particle interior or linear polymer interior is substantially compromised or prevented completely such that the optimal maximum swell ratios of up to 100× are seldom achieved. To counteract this restriction of surface swelling, substantial amounts of cellulose fibers have been included in many products so as quickly to absorb and distribute the fluid for eventual supply to the SAP particles. Commonly used are absorbent cotton fibers and compositions thereof.
In addition, inert inorganic substances having large surface areas are known to have slight absorbent properties. These secondary components are hydrophilic, inorganic minerals, such as microporous alumino silicate minerals or other volcanic scoriaceous materials. Particular examples include: molecular sieves; bentonite clays, such as aluminum phyllosilicates; and montmorillonite clay, or sodium bentonite; or zeolites such as analcime, chabazite, clinoptilolite, heulandite, natrolite, phillipsite, or stilbite. Exemplary commercially available materials are the bentonite Texas Sodium Bentonite, available from Texas Sodium Bentonite, Inc., of Comanche, Tex., and the St. Cloud Natural Zeolite, which is a natural clinoptilolite form of potassium aluminosilicate, available as powders and granules from a number of sources including GSA Resources, a subsidiary of St. Cloud Mining Company of Winston, N. Mex. These solid alternate phase carriers are commercially available in various particle sizes.
Additionally, materials showing slight absorbent properties are available from Cabot Corporation which supplies a number of different fumed silica products suitable for use in the invention compositions. These include various products with a large hydrophilic surface area: Cab-O-Sil™ EH-5 (380 m2/g of surface area), Cab-O-Sil™ HS-5 (325 m2/g of surface area), Cab-O-Sil™ M-5P (200 m2/g of surface area), Cab-O-Sil™ M-5 (200 m2/g of surface area), Cab-O-Sil™ PTG (200 m2/g of surface area), Cab-O-Sil™ MS-55 (255 m2/g of surface area), Cab-O-Sil™ LM-150 (160 m2/g of surface area).
Fibrous materials such as cloth have been employed to remove undesirable water remaining due to leakage or flooding. Again, absorption is minimal at best, generally <2×. Alternatively, excess water can be vacuumed. However, when the amount of water is large, these methods are inefficient and time consuming.
Traditionally, sandbags, filled with sand, have been used to prevent water from egressing into occupied areas of homes and businesses. They have also been used to prevent the overflow of rivers, lakes, marshes, etc. The weight and volume of conventional sandbags makes them difficult to transport. Water absorption by sandbags is minimal. Thus, “sandless sandbags” using the above mentioned SAP components (without however added inert inorganic substances such as bentonite or zeolites, or fumed silica or other fibrous polymers like starch) have been developed to circumvent some of these problems. These are typically comprised of a polyacrylic acid powder without filler to aid in absorbing of water and may include the same fabric material used in baby diapers or tampons. The outer bags, exposed to the environment, themselves are made of traditional materials, including burlap, polyester, polypropylene, or nonwoven polymers.